<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
      var obj =   Object.assign({},{name:"张三",age:20},{age:32,height:"178cm"});
     console.log(obj);


        function fn(a){
            a = a ?? 1;  // ES2020--->ES11
            // ES6--->ECMAScript2015
            console.log(a);
        }

        fn("");
        // ES8 async await
    </script>
</body>
</html>